An inkjet recording apparatus is well-known in which ultraviolet rays are radiated onto ultraviolet curable ink which was ejected from recording heads onto recording media, so that the ultraviolet curable ink is cured on the recording media.
In Unexamined Japanese Patent Application Publication No. 2005-254560, an inkjet recording apparatus is disclosed in which a plurality of LEDs (which are light-emitting diodes) are aligned as ultraviolet ray radiating devices. The radiating device using the LED is superior to other radiating devices, such as a mercury lamp or a metal halide lamps with respect to miniaturization and response characteristics, which will be described below.
Concerning the miniaturization, a reflector is essential to effectively radiate the rays from the mercury lamp radiating device, while a reflector is not essential for the LED radiating device. Further, in the LED radiating device, LEDs can be aligned at high density.
Concerning the response characteristics, to wait until the amount of radiating rays become stable is essential for the mercury lamp radiating device, while the LED radiating device can be quickly turned on and off. Due to this, the LED radiating device can be used for an inkjet recording apparatus working as an on-demand apparatus.
Unexamined Japanese Patent Application Publication 2006-19676 discloses an inkjet recording apparatus employing a light source unit in which a heat-sink is provided on a semiconductor element, because in a semiconductor light emitting elements, such as the LED and a semiconductor laser, the heat release value is so great that deterioration of the semiconductor light emitting elements is significant. Cooling water is made to flow through the heat-sink to cool the semiconductor light emitting elements.
Further, Unexamined Japanese Patent Application Publication 2006-19676, discloses a light source device in which a plurality of the light source units are aligned to radiate high output light.
Still further, as shown in FIG. 10 of Unexamined Japanese Patent Application Publication 2006-19676, to align a plurality of the light source units, a flow channel is structured in which cooling water, which has passed through one light source unit, enters the next light source unit. Due to this structure, water, heated by an upstream light source unit, is supplied to a downstream light source unit.
The semiconductor light emitting elements have characteristics in which the temperature dependency of luminescence intensity is very great. Accordingly, when the temperature differs in the cooling water of the upstream and downstream light source units as described above, cooling water absorbs different amounts of heat from each unit, so that the temperature of each semiconductor light emitting element differs, which results in a differing amount of light emitted between from each semiconductor light emitting element.
If the light source device, including a plurality of said light source units, is applied onto the ultraviolet ray radiating device of Unexamined Japanese Patent Application Publication No. 2005-254560, the following problems will be generated.
For example, in a case that the light source device is moved to scan the recording media, perpendicular to an aligned direction of the plurality of light source units, since the luminescence intensity differs between the light source units, ink curing condition will differ on portions of the recording media which face different light source units. If said ink curing conditions differ, the glossiness of the cured ink differs, which results in an uneven image (being uneven glossiness) striated in the scanning direction.